A 2 pA/√Hz Input-Referred Noise TIA in 180-nm CMOS With 2.5 GHz Bandwidth for Optical Receiver

This letter describes an ultralow-noise, high-speed transimpedance amplifier (TIA) applied to the analog front-end (AFE) circuit of the high-sensitivity optical receiver. A combination of a three-stage amplifier and two positive feedback Miller capacitors is introduced to comprehensively reduce the input-referred noise current (IRNC) of a shunt-feedback TIA (SFTIA) and to extend its bandwidth (BW). The proposed SFTIA utilizes an 80 K $\Omega $ resistor as the feedback resistor (RF) and achieves a BW of 2.5 GHz and an average IRNC of only 2 pA/ $\surd $ Hz in 180 nm CMOS technology, which is the lowest TIA noise reported to date above the GHz BW. Although the fabrication process is not as advanced as the state-of-the-art process, we believe it remains valuable and instructive for a wide variety of applications requiring low noise and high sensitivity.